Backing agent for carpet

ABSTRACT

A backing agent for adhering a carpet backing to a carpet comprising 1. A MIXTURE OF ABOUT 90 TO 20 PERCENT BY WEIGHT OF ATACTIC POLYPROPYLENE AND ABOUT 10 TO 80 PERCENT BY WEIGHT OF A URETHANE PREPOLYMER HAVING AN ISOCYANATE GROUP AT THE TERMINALS OF THE MOLECULE, AND 2. ABOUT 5 TO 60 PERCENT BY WEIGHT OF AN INORGANIC FILLER BASED ON THE TOTAL WEIGHT OF THE MIXTURE AND THE INORGANIC FILLER.

United States Patent [191 Uchigaki et al. [4 Dec. 23, 1975 BACKING AGENT FOR CARPET 3,312,755 4/1967 Cappuccio et a1. 260/859 R 75 Inventors: Taku Uchigaki; Masataka Noro,

both of Mie, Japan Primary Examinerl ewis T. Jacobs 73 Assignee: Mitsubishi Petrochemical 00., Ltd., .""Z "Q f" Rmhwen,

Tokyo, Japan acpe [22] Filed: Sept. 3, 1974 21 Appl. No.: 502,339 1 ABSTRACT A backing agent for adhering a carpet backing to a [30] Foreign Application Priority Data carpet comprising i Sept. 3, 1973 Japan 4888221 1, a mixture of about 90 to 20 percent by weight Of atactic polypropylene and about 10 to 80 percent by Cl 260/4239; 260/ 4 /859 R weightof a urethane prepolymer having an isocyanate [51] Int. GL2 C08K 3/34; CO8K 3/26 group at the terminals of the molecule, and [58] m of Search 260/4239 859 R 2. about 5 to 60 percent by weight of an'inorganic [56] u v References Cited I tiller based on the total weight of the mixture and the inorganic filler. UNITED STATES PATENTS v 3/1967 Steingiser et'al 260/859 v 6 Claims, 2 Drawing Figui'es- BACKING AGENT FOR CARPET BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to an improvement in a backing agent for a carpet backing, and, more specifically, to an improvement in a backing agent of the hot melt type to be coated on the back surface of carpets such a Wilton carpet or a needle-punched carpet or to be applied between the carpet pile and a second backing.

2. DESCRIPTION OF THE PRIOR ART As a backing agent, i.e., a bonding and coating agent, in use on carpets and rugs, (a) a latex-type backing agent comprising a dispersion in water of a natural or synthetic rubber latex as a main constituent, a curing agent for the latex and a filler such as calcium carbon ate, or (b) a hot melt-type backing agent comprising mainly a thermoplastic synthetic resin, for example, atactic polypropylene, low density polyethylene, an ethylene/vinyl acetate copolymer and so on, is gener ally used. Both of these backing agents (a) and (b) have disadvantages, and are not entirely satisfactory.

Since the backing agent (a) is used in the form of an aqueous dispersion, it is necessary to remove water, by drying after the backing agent is applied to a woven carpet material. Because of the necessity for this drying step, instantaneous bonding not only is unexpected but also carpet productivity is reduced. Furthermore, a large size heating device is often required.

On the other hand, backing agent (b) has the advantage that the speed of production is high because with the use of backing agent (b) the drying step can be omitted and instantaneous bonding can be effected by solidifying the melted backing agent. However, use of backing agent (b) has the defect that the bonding strength in practical use after a few weeks have passed from carpet fabrication is poorer than when backing agent (a) is used.

In order to impart elasticity and higher weight to the carpet and also to reduce the cost of the backing agent, an inorganic filler is often added to the'backing agent. Where the viscosity of the backing agent increases as the amount of the filler added increases, the backing agent must be heated to a high temperature until it has sufficient flowability for use. Conversely, if the amount of the filler is reducedin order to facilitate coating at low temperatures, the fabricated carpet lacks weight and elasticity. Especially where the warp and weft yarns of the base cloth of a carpet are made of stretched products such as polypropylene yarns as shown in the accompanying drawings, the stretched product shrinks when a backing agent is applied at a temperature higher than 130C. As a result the base cloth is deformed. The inorganic filler cannot be added in large quantities to a backing agent since the backing agent must have a sufficient viscosity to pennit coating at low temperatures.

Thus, the water dispersion-type latex backing agent (a) is now in widespread use because of its low cost, in spite of the fact that a reduction in productivity occurs when this type of backing agent is used as a bonding and coating agent for bonding a backing to a woven carpet material.

SUMMARY OF THE INVENTION It is an object of this invention, therefore, to provide a backing agent, as a bonding and coating agent, for a.

2 carpet backing, which is free from the above described defects of conventional backing agents for a carpet backing; This invention provides a backing agent for a carpet backing comprising l. a mixture of about 90 to 20 percent by weight of atactic polypropylene and about 10 to percent by weight of a urethane prepolymer having an isocyanate group at the terminals of the molecule, and

2. about 5 to 60 percent by weight of an inorganic filler based on the total weight of the mixture and the inorganic filler.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a tufted carpet, in which reference numeral 1 represents a pile yarn; 2, a weft yarn; 3, a warp yarn; and 4, a layer of a backing agent.

FIG. 2 is a vertical sectional view of a tufted carpet,

in which the reference numerals l, 2, 3 and 4 are the same as in FIG. 1 and 5 represents a second backing.

DETAILED DESCRIPTION OF THE INVENTION The invention will be described in greater detail below.

The urethane prepolymer having an isocyanate group (-NCO) at the terminals of the molecule is used in a proportion of about 10 to 80 percent by weight with about to 20 percent of atactic polypropylene. The urethane prepolymers which can be used in this invention have a molecular weight of about 1,000 to 10,000, a mean molecular weight of about 3,500 and an amine equivalent of about 1,100 to 1,200. This urethane prepolymer is obtained by condensation polymerization of at least one diisocyanate compound and at least one diol compound in the presence of a condensing agent such as, for example, stannous octoate, triethylenediamine, dibutyl tin dilaurate, etc.

The diisocyanate compounds which can be employed in this invention have a molecular weight of about 168 to about 400, and also can be represented by the following general formula,

oCN R NCO wherein R represents an aliphatic group or an aryl group, preferably an aryl group. Examples of diisocyanate compounds which can be used are 1,5-naphthylene-diisocyanate, 3,3-dimethyldiphenyl-4,4- diisocyanate (toluene diisocyanate), 4,4-diphenylmethane diisocyanate, 3,3-dimethyldiphenylmethane- 4,4-diisocyanate, polymethylenepolyphenyl-isocyanate, l ,3-dimethylbenzol-4,6-diisocyanate, 1,4- naphthylene-diisocyanate, 3 ,3 -dimethoxybiphenyl- 4,4 '-diiso cyanate, 2-nitrobiphenyl-4 ,4 '-diisocyanate, 2,2-dimethyldiphenylmethane-4,4'-diisocyanate and hexamethylenediisocyanate. These compounds can be used either alone or in admixture.

The diol compounds which can be employed in this invention have a molecular weight of about 62 to about 4,000, and also can be represented by the following general formula,

mom.- wherein R represents an aliphatic group. Examples of suitable diol compounds are monomers or polymers of ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, l,4-butynediol and trimethylol propane, and polytetramethylene ether glycol. These diol compounds can be used either alone or in admixture.

Preferred urethane prepolymers have a Brookfield viscosity of at least about 300,000 centipoises but not higher than 2,500,000 centipoises at C. A suitable molar proportion of the diisocyanate compound to the diol compound ranges from about 1.8 l to 2 l.

The isocyanate groups at the terminals of the molecule induce a molecular chain extending reaction with moisture in the air after the bonding agent'is applied. The reaction is shown below by schematic (1). This reaction causes the molecular weight of the urethane prepolymer to increase and the backing agent to increase in cohesive force. Furthermore, as is shown by the following schematic (2), if the base material of the carpet has an active hydrogen atom, the terminal isocyanate groups further increase the bond strength in the interface between the carpet base material and the carpet backing.

4 ally about 0.1 to microns, preferably 0.1 to 7 microns.

A suitable tacky resin such as a perpene-phenol copolymer resin, a petroleum resin, rosin or a wax can be added to the above three ingredients in order to adjust the resiliency of the carpet or impart suitable permeability to the pile fabric. The tacky resin can be present in an amount of up to about 25 percent by weight, preferably below 10 percent by weight based on the weight of the polymer in the backing agent used.

The ratio of the urethane prepolymer to the atactic polypropylene is adjusted to about 10 to 80 90 to 20 (percent by weight) in this invention. 1f the concentration of the atactic polypropylene is less than about 20 percent by weight, instantaneous bond strength between a pile fabric or the like and a cellulosic first backing such asjute or the like is weak. Accordingly, it

(urethane prepolymer) (rendered high-molecular weight) carpet hacking interface carpet substrate) carpet backing) (carpet back surface/ carpet hacking interface) 1 In the backing agent of this invention, atactic polypropylene is used in a proportion of about 90 to 20 percent by weight with the urethane prepolymer. The

atactic polypropylene comprises mainly atactic polypropylene (APP) expressed by the rational formula -(-CH CHR)-,,(in which R is CH;,) which comprises a major proportion of a non-crystalline amorphous portion and in which the substituent is in a random steric arrangement. Preferably, ,the atactic polypropylene used in this invention has a specific gravity of about 0.8 to 0.9, a molecular weight of about 2,000 to 100,000, preferably 7,000 to 50,000, n-heptane soluble parts of about 100 percent, an intrinsic viscosity, [1;], of about 0.27 to 0.40, which'is measured in tetralin at 135C, and a softening point of about 90 to 150C. Since the atactic polypropylene is produced as a by-product in the polymerization of propylene, and is available at low cost, the use of atactic polypropylene is commercially advantageous. l

The bonding agent of thisinvention isprepared by adding a non-porous inorganic filler to a mixture of the above-described urethane prepolymer having isocyanate groups at the terminals and the atactic polypropylene. The inorganic filler is added in an amount of about 5 to percent, preferably 10 to 45 percent, by weight based on; the total weight of the mixture and the inorganic filler. Examples of suitable inorganic fillers which can be used are CaCO 'Al(OH)3, clay and talc, with CaCQ, and AI(OH);, being preferred. The inorganic filler can be used either alone or as a mixture thereof. The average particle size of the inorganic filler is gener- (carpet back surface/carpet backing interface: rendered high-molecular weight) is impossible to cut the resulting carpet to the desired size immediately after its preparation. On the other hand, if the concentration of the atactic polypropylene is above about percent by weight, the concentration of the urethane prepolymer is reduced, andtherefore, the peel strength after a few weeks between the pile fabric and the jute at a temperature of 60C is weak. This poses a problem during the use of the carpet. Furthermore, if the proportion of the urethaneprepolymer is less than about 10 percent by weight, long periods of time are required for moisture absorption and curing, and a firm bond strength in practical use cannot be obtained.

The proportions of the atactic polypropylene and the isocyanate-terminated urethane prepolymer are determined on the above basis.

The proportion of the inorganic filler is limited to about 5 to 60 percent by weight based on the total weight of the mixture of the atactic polypropylene and the isocyanate-terminated urethane prepolymer and the inorganic filler. If the proportion of the inorganic filler is less than about 5 percent by weight, the carpet does not exhibit a high weight. Furthermore, the backing agent becomes expensive. On the other hand, if the Since the backing agent of this invention exhibits a continued very high bond strength and can be easily applied, the Parts excellent advantage of providing carpets at low cost 70C) and in great quantities with improved productivity can 5 Paral'fin Wax (I 15F grade) 30 be obtained. The backing agent of this invention can be applied to the carpet at a temperature of about 100 to 130C such that the carpet pile, e.g., polypropylene, fabric is not affected, and at a viscosity of about 3,000 to 10,000 cps, and then if a backing such as a jute 10 backing is to be adhered, the backing simply contacted "-"Vinyl acetate content about Ill mol'/.

COMPARATIVE EXAMPLE 3 (hot-melt type) with the applied backing agent layer and thereby ad- Parts hered thereto' Ethylene/Vinyl Acetate Cnpolymer I00 The backing agent of this invention can comprise a (Same as Comparative Example 2) layer as shown in the embodiment in FIG. 1 or can be lgfi'gf? Ester (smcmng 80 POI used as a bonding agent to bond at second backing as p m w21x 15F grade, 2o shown in the embodiment in FIG. 2. Further the back- Calcium Curbanatc ing agent can be used to bond to carpets and baekings of generally any type made of any material such as wool, polyamide, polypropylene, rayon, polyester, jute,

etc.

The invention will be illustrated more specifically by COMPARATIVE EXAMPLE 4 (hot-melt type) Parts reference the following Examples. Unless otherwise 1 Atactic Polypropylene (softening point: ind cated, all parts, percents, ratios and the like are by 25C; so: 09; molecular weight: '00 weight. 30.000 to 35000 Petroleum Resin (softening point 80C) I00 EXAMPLES I AND 2 AND COMPARATIVE "Petrosin No. 80 roduced h' Mitsui Petrochemical (o.. Ltd. EXAMPLES 1 TO 5 s P Each of the backing agents indicated in Table l was used to bond a pile fabric (of isotactic polypropylene yarn shrinking at about 135C) to a jute backing at COMPARATIVE EXAMPLE 5 (hot-melt type) each of the coating temperatures indicated in Table l. pam

The pile yarn pulling strength and the peel strength i Ammic polypmpylcnc (Same asthu [00 between the pile fabric and the ute backing were meaused in C m fl Exumpksured, and the results obtained are shown in Table l. Petroleum t tesin (softening point we) I00 The amount of the backing agent applied was 1000 Example 4) [00 g/m in each case. The pile yarn pulling strength was 40 measured by means of a Shopper tensile tester at a tensile speed of 300 mm/min. The peel strength he tween the pile fabric (isotactic polypropylene) and the EXAMPLE 1 (Present Invemlon) jute backing was measured at 90 at a tensile speed of 300 mm/min. using an Instron autograph tensile tester. Pam The compositions of the backing agents used were as Ataetie Polypropylene (same as that 100 used in Comparative Example 4) Urethane Prepolymer containing -NCO at the terminals of the Molecule (an addition polymerization product between toluene diisocyanate and polypropylene glycol; viscosity about 300,000 cps;

follows:

COMPARATIVE EXAMPLE 1 (latex type) 50 s mean molecular weight about 3.500; amine Carhoxyl-Modified SBR Latex) 100 'Y 7h: Oxide 5 Calcium Carbonate (average particle I00 S'mjium pvmphmpham 1 5 diameter: about 0.5 to 5.0 microns) Calcium Carbonate 200 Water 7 90 EXAMPLE 2 (Present Invention) "'(roslene SA No. 20, a earboxyl modified styrene-hutadiene latex having a viscosity of about 3.500 eps at 25C produced by 'I'ak eda Chemical Industries. Ltd.

Parts 7 Ataetic Polypropylene (same as that I00 vi used in Comparative Example 4) COMPARATIVE EXAMPLE 2 (hot-melt type) Urethane Prepolymer (same as that used 50 S in Example I) Calcium Carbonate (same as that used I50 Parts in Example I Ethylene/Vinyl Acetate C( molymer I V I00 Rosin Glycerin Ester (softening point Table l Coating Tem Pile Yarn Peel Strength between perature (C) Pulling Pile Woven Fabric and (viscosity Strength Jute Backing (Kg/inch) Samples in cps) (Kg) Below C Below 60C Comparative Room Example 1 Temperature 3.0 2.0 1.2

(20.000) Comparative 200 1.5- I L5 0.] Example 2 (40.000) Comparative 200 l.() 1.0 0.1 Example 3 100,000) Comparative 180 l .0 0.8 0.] Example 4 (6,000) Comparative I80 0.9 0.6 0.05 Example 5 (20000) Example l 120 3.5 2.7 L8

(6,000) Example 2 120 3.2 2.5 1.7

EXAMPLES 3 TO 5 AND COMPARATIVE -Ontinued EXAMPLES 6 AND 7 l While the amount of calcium carbonate was maintained at 50 percent by weight based on the total weight of the inorganic filler and the mixture of atactic polypropylene (as described in Comparative Example 4) and the urethane prepolymer (as described in Example l), the ratio between the atactic polypropylene and the urethane prepolymer was changed as shown below.

Each of the backing agents was used in the same way as in Examples 1 and 2, and the pile yarn pulling strength COMPARATIVE EXAMPLE 6 Parts Parts Ataetic Polypropylene Urethane Prepolymer Calcium Carbonate COMPARATIVE EXAMPLE 7 Parts and the peel strength were measured in the same way. 35 The results obtained are shown in Table 2.

Table 2 Viscosity at Pile Yarn Peel Strength between the Time of Pulling Pile Woven Fabric and Coating Strength Jute Backing (Kg/inch) Samples (cps/I20C) (Kg) Below 20C Below 60C Comparative I00.000 l .5 0.6 0.3 Example 6 Example 3 l00,000 2.2 2l L8 Example 4 4.500 3.8 30 2.2 Example 5 2.500 4.0 30 30 Comparative 2.000 4.0 3.0 3.0 Example 7 EXAMPLES 6 TO 8 AND COMPARATIVE COMPARATIVE EXAMPLE 6 EXAMPLES 8 AND 9 l Parts I 55 A backing agent was prepared from parts of negro y atactic polypropylene (as described in Comparative Calcium Carbonate l 50 Example 4) and 50 parts of a urethane prepolymer (as described in Example 1 and calcium carbonate in the EXAMPLE 3 Parts amount shown ln Table 3 below. Thus, the welght ratio l v Amcfic pnlypmpylene 9O of the atactlc polypropylene to the urethane prepoly Urethane Prepolymer l() mer was 2: l, and the proportion of the calelum carbon- Calcium cflrbuflflte ate based on the total weight of the atactic polypropyl- EXAMPLE 4 ene, the urethane prepolymer and the calcium carbon- I Parts ate varied from about 3 percent to 70 percent. Each of Amen-C polypmpylcne 40 65 the bonding agents was applied in the same way as in Urethane Prepolymer 60 Examples 1 and 2 and the plle yarn pulling strength and Calcium Carbonate 50 EXAMPLE 5 the peel strength were measured in the same way. The results obtained are shown in Table 3 below.

Table 3 Amount Viscosity Pile Yarn Peel Strength beof Calciat the Pulling tween Pile Woven urn Carbo Time of Strength Fabric and Jute nate Coating Backing (Kg/inch) Samples (parts) (cps/120C) (Kg) Below 20C Below 60C Comparative 4 3,700 40 30 2.2 Example 8 Example 6 8 3,800 4.0 3.0 2.2 Example 7 40 4,500 3.7 2 7 1.8 Example 8 225 45,000 2.1 2.0 1.2 Comparative 350 100,000 I .1 0.4 0. 1 Example 9 be apparent to one skilled in the art that variouschanges and modifications can be made therein'without departing from the spirit and scope thereof.

What is claimed is: l l. A backing agent for adhering a carpet backing to a carpet comprising v l. a mixture of about 90 to 20 percent by weight of atactic polypropylene having a molecular weight of 2,000 to 100,000 and about 10 to 80 percent by weight of a urethane prepolymer having a-molecular weight of 1,000 to l'0,000,an amine equivalent of about 1,100 to 1,200 and-having an isocyanate group at the terminals of the molecule, and I 2. about 5 to 60 percent by weight of a non-porous inorganic filler based on the total weight of said mixture and said inorganic filler, said backing agent having a viscosity when applied of 3,000 to 10,000 cps and said ureth'ane. prepolymer being an addition polymerization productbetween at least one diisocyanate compound having an isocyanate group at the terminals of the molecule and 'a't least one diol compound.

2. The backing agent of claim 1, wherein said atactic polypropylene has a specific gravity of about 0.8 to 0.9, a molecular weight of about 2,000 to 100,000 and a softening point of about to 1509C.

3. The backing agent of claim 1, wherein said urethane prepolymer has a viscosity of about 300,000 to 2,500,000 centipoises at 25C. I

4. The backing agent of claim 1, wherein said diisocyanate compound is selected from the group consisting of l,5-naphthylenediisocyanate, 3,3-dimethyldiphenyl-4,4'-diisocyanate, 4,4"-dipheny1methane-diisocya- 

1. A BACKING AGENT FOR ADHERING A CARPET BACKING TO A CARPET COMPRISING
 1. A MIXTURE OF ABOUT 90 TO 20 PERCENT BY WEIGHT OF ATACTIC POLYPROPYLENE HAVING A MOLECULAR WEIGHT OF 1,000 TO 100,000 AND ABOUT 10 TO 80 PERCENT BY WEIGHT OF A URETHANE PREPOLYMER HAVING A MOLECULAR WEIGHT OF 1,000 TO 10,000, AN AMINE EQUIVALENT OF ABOUT 1,1000 TO 1,2000 AND HAVING AN ISOCYANATE GROUP AT THE TERMINALS OF THE MOLECULE, AND
 2. ABOUT 5 TO 60 PERCENT BY WEIGHT OF A NON-POROUS INORGANIC FILLER BASED ON THE TOTAL WEIGHT OF SAID MIXTURE AND SAID INORGANIC FILLER, SAID BACKING AGENT HAVING A VISCOSITY WHEN APPLIED OF 3,000 TO 10,000 CPS AND SAID URETHANE PREPOLYMER BEING AN ADDITION POLYMERIZATION PRODUCT BETWEEN AT LEAST ONE DIISOCYANTE COMPOUND HAVING AN ISOCYANATE GROUP AT THE TERMINALS OF THE MOLECULE AND AT LEAST ONE DIOL COMPOUND.
 2. about 5 to 60 percent by weight of a non-porous inorganic filler based on the total weight of said mixture and said inorganic filler, said backing agent having a viscosity when applied of 3,000 to 10,000 cps and said urethane prepolymer being an addition polymerization product between at least one diisocyanate compound having an isocyanate group at the terminals of the molecule and at least one diol compound.
 2. The backing agent of claim 1, wherein said atactic polypropylene has a specific gravity of about 0.8 to 0.9, a molecular weight of about 2,000 to 100,000 and a softening point of about 90* to 150*C.
 3. The backing agent of claim 1, wherein said urethane prepolymer has a viscosity of about 300,000 to 2,500,000 centipoises at 25*C.
 4. The backing agent of claim 1, wherein said diisocyanate compound is selected from the group consisting of 1,5-naphthylenediisocyanate, 3,3''-dimethyldiphenyl-4,4''-diisocyanate, 4,4''-diphenylmethane-diisocyanate, 3,3''-dimethyldiphenylmethane-4,4''-diisocyanate, polymethylenepolyphenyl-isocyanate, 1,3-dimethylbenzol-4,6-diisocyanate, 1,4-naphthylene-diisocyanate, 3, 3''-dimethoxybiphenyl-4,4''-diisocyanate, 2-nitrobiphenyl-4,4''-diisocyanate, 2,2''-dimethyldiphenylmethane-4,4''-diisocyanate, and a mixture thereof.
 5. The backing agent of claim 1, wherein said inorganic filler is calcium carbonate, aluminum hydroxide, clay or talc.
 6. The backing agent of claim 5, wherein said inorganic filler has an average particle size of about 0.1 to 30 microns. 